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Thread: Looper exhaust porting
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11-22-2013, 05:38 AM #1
Looper exhaust porting
If I make my exhaust ports (bridgeport looper)wider, would that make low end torque suffer?
I want to shape them like a letter "L", turned upside down...
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11-22-2013, 09:35 AM #2
If you just widen them, you'll make everything better. Just don't raise them unless you know exactly what you're doing.
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11-22-2013, 12:00 PM #3Scream And Fly VIP
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.150 wider at the top and taper to orginal at the bottom but unless you do the right intake work it will not add any power
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11-22-2013, 12:28 PM #4
Thanks Racer!, will do that!
The right "intake-work" are you referring to changes in duration on transfer/boost ports?
I have already cleaned the intake mainfold up - taken away all sharp corners and added CCMS reeds. What is your opinion on shaving the heads? Boat is appx 2200lbs, prop is 22"raker, boat mainly used for skiing and recreation, no long wot-runs, maybe a minute max. I want to be able to use 91octane.
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11-22-2013, 10:15 PM #55000 RPM
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11-24-2013, 02:20 AM #6
A couple of questions;
.150 must be like 4mm, anyone to confirm?
still trying to learn the inch system...
When you guys write .150, you mean 0,150 of an inch -right?
Any good tricks concerning cleanup after porting and honing?
compressed air, what else?
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11-26-2013, 08:41 PM #77000 RPM
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11-26-2013, 12:20 PM #85000 RPM
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11-26-2013, 12:46 PM #9Scream And Fly VIP
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.150 wider on each exhaust port at the top, make sure you radius them when finished. Clean up the rod slot and match the intakes being careful to maintain original angle since you are not looking for a high rpm engine.
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11-26-2013, 12:57 PM #105000 RPM
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Just starting a v4 looper for a 15' allison,
Any thing different on the V4 ?
Will the V8 Finger ported piston w/ block mods work ok in the V4, or is there a better direction ?Last edited by thornl01; 11-26-2013 at 01:02 PM. Reason: spell
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11-26-2013, 01:44 PM #11
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11-27-2013, 04:43 PM #12
Clean up the rod slot...
on small high revving case-fed motors, I have ported/created a "direct passage" from the crankcase(rodslot)to the transfer boost/aux-port, this procedure has been succesful by allowing the fresh charge to enter direct into the boostport as soon as the piston starts its upgoing movement.
Do you have any experience of this on outboards? In this case the boost port don't have to rely on the piston-window...
The yellow tape in the pic is an attempt to describe my idea
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11-30-2013, 10:54 AM #13
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05-27-2014, 05:59 PM #14
Does anyone know what the max PSI for a blue printed V8 should be? Before we blue printed and evened out the ports on it the PSI was 135, this is an original 3.6 punched out to 4.0 liters. We now have 150-152 psi after raising the ports and the motor has not been broke in yet , only about 30 minutes at the dock, and this is with stock 4 liter heads, I have a pair of Taylor Marine and Machine heads and I am afraid to put the on with the PSI at this level? anyone? I have been told that the max PSI should be 145 to 155, but I have also been told that stock V6's are usually 150...HELP!!!!
1987 Switzer GL-21 OMC V8 Prototype/ Replaced by another V8
1983 Switzer SS-20-C/Evinrude V6
1983 Switzer SS-20-B under renovation
1972 Switzer "Flatback Transom" Super Sport (in storage to be rebuilt at another time)
Replica 1964 Switzer Playboy 1968 125hp Merc Short Shaft
1977 Switzer Super Sport**sold** Reaquired on Sept.29,2016
Join us at The Switzer Regatta & Hot Boat Rally
https://www.facebook.com/switzer.craft.7
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05-27-2014, 07:05 PM #15
Are you checking the compression with the same guage? Porting can only lower the compression. Unless you ended up with a bigger cc' dome or the 4.0L heads have smaller cc' chambers than the 3.6L heads then the only gain in compression should be from a fresh bore and rings.